what causes this?

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I have been practicing MIG now for a while, and my beads look pretty good, but when i cut across butt joints i always have little pin holes in the root. I have tried everything i can think of and nothing seams to have an effect.1. lower amps2. higher / lower feed3. weave / no weave4. more / less gas5. push/pullhere is a sample:1/8" thick A36C25 at 25cfm130 amps (max on my machine).030" weldmark ER70S-6 wire at 260 - 280 ipmno weave, pull
Reply:I don't think we can ever expect a mig weld to have 100% perfect solidity, with no air in it at all. There is no bed of flux like sub arc welding, and there is a lot going on all at once- the filler is carrying the arc, it has to do 2 jobs at once, plus the gas you are adding into the equation. Those welds look very good. Now, with that said, I already hear the peanut gallery running to their keyboards to jump me.... I am not saying a porous weld is a good thing. I just personally think it would be unrealistic to believe there would be no gas pockets of any kind in the weld, ever. And, I don't feel that if a tiny gas pocket was created it would mean the weld was not sound, or that the weld would not be capable of holding air pressure. Maybe some pipeline welders will give some insight on any possible way to try to eliminate the gas pockets in question.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:its lack of fusion/ penetration. your not getting the weld all the way in there.  turn upp the heat and it should go away.
Reply:I'm maxed out on the heat setting. Is more heat really needed?the bead I'm laying is 3 inches long, so i lay a 3 inch bead flip the part around and lay a bead down the back side. Half way down the back side the base metal is glowing red hot a good inch to an inch and a half out from the bead. It's soft enough that i have to be careful as i finish up or i can blow out the edge.
Reply:I was sorta thinking its a fusion problem too... look at where your problems are, thats directly at the root of the weld.I like to party!
Reply:That is a pretty good looking weld. Polish it and etch it you will see much better what you have done.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Can't speak for others but I've never seen nor have worked to a MIG spec that required 100% solid weld. There's always been a maximum amount of defects allowed per square inch set up by the engineers that designed any given peice. Most of my MIG experience didn't even have that, pass the DT/NDT tests and you were in. Some stuff got random checks but most was "field tested"...lolAnything worth doing is worth doing RIGHT
Reply:Lack of fusion.  You haven't burned into the root at all.  Are you weaving your first pass?  Try running your first pass directed straight at the seam with no weave then run a cover pass.  I've seen that before with migs when the root pass was weaved and it basically bridged the seam rather than melting it.  Also looks like you may need to bevel the edges if you are wanting 100% penetration.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Originally Posted by Hammack_WeldingLack of fusion.  You haven't burned into the root at all.  Are you weaving your first pass?
Reply:Howdy Dan S no expert here, the first thought was the general size and shape of the fillet seems like the length of the leg is a little long compared to the thickness of the material and the profile seems a little rounded (convex).  I read you are useing .030 for 1/8 and maxed on you amps as an experiment you might try .023 the thought is you may be able to slow down and not carry as much deposition (puddle sixe) thus gain greater penetration at the root. Don't know your travel angle but straight on may lead to better penentration and flatter profile.
Reply:Originally Posted by wielroI read you are useing .030 for 1/8 and maxed on you amps as an experiment you might try .023 the thought is you may be able to slow down and not carry as much deposition (puddle sixe) thus gain greater penetration at the root.
Reply:If you got into globular with .023 then the voltage was set too high.  Either that or you may have mistaken globular for insufficient wire feed speed.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:As an experiment bevel the standing part before tacking together.  To expect penetration right into the corner is not realistic considering the process you are using.  I never expect to penetrate any joint unless I do a bevel preparation of some sort.  Thinking you have enough heat to get to the bottom of a tight crack or joint is optimistic.  As said before.. for the thickness your fillet is massive.
Reply:Looks like a very good weld, although it would be nice to get that last little bit of fusion at the root.  This is technically a lack of fusion at the root, and the weld size may be too large for the plate thickness (maybe a little too slow on travel).  Short arc is inherently prone to this, it is difficult to get good fusion down to the root.  It will be very interesting to see an etched cross section to see how far the weld penetrates the side walls.My experience is primarily with pulsed spray MIG, but I guess I would look at running a tighter tip-to-work distance if possible, don't know what you are running now, but less stickout will increase the amperage and penetration. With pulsed spray I'd run a stickout as tight as 1/2".  Also, since you have a 115V machine with limited output, are you running a long extension cord, or is the machine a long distance from the main breaker, because the max output will drop with the increased voltage drop of a long supply lead.Make sure the wire tip and arc are directly pointed at the root.  And with a drag or push angle, anything too far from 90 degrees will reduce the energy density of the arc.  With the pulsed spray, I run a push angle, and stay on the leading edge of the puddle with the travel speed, this give a nice flat weld contour, but with short arc I believe it is recommended to drag for increased penetration, but again I think you need to stay on the leading edge of the puddle since riding too far back on the puddle will tend to cushion/block the arc penetration.Beveling the joint will reduce the unfused portion of the joint at the root, but you may still see a bit of lack of fusion because the bevel is now a even tighter notch to try to get the arc down into.  Generally a "T" joint fillet weld is not beveled and only requires complete fusion along each leg.Last edited by pulser; 03-11-2008 at 02:37 PM.
Reply:yes you need more heat but if your machine is maxed...you say you pulling so definately push the gun so it will preheat as you weld a little as well as gouge som material out ahead of the puddle.
Reply:Originally Posted by welder155yes you need more heat but if your machine is maxed...you say you pulling so definately push the gun so it will preheat as you weld a little as well as gouge som material out ahead of the puddle.
Reply:OK, i tried the acid etch and it kinda worked... i could see it with my eye, but the contrast wasn't great enough for me to get a good picture of it.since i couldn't get a good pic of it i sketched this out quick. some times i got a lot of penetration some times i got a little. i would say most of the time penetration was 1/4 to 1/2 the way into the base metal.on every cross section penetration was zero at the root. This kind of sounds like  what a lot of you are suggesting (an issue with the short circuit transfer method).
Reply:ok yes slightly foward if not straight in.  also it sounds wrong but try to slow the wire down and travel slower to let it soak in.
Reply:I was wondering if you were running an extension cord? Also wondering if you were grinding of the mill scale?  If you were running a cord I would try to keep it as short as possible, making yor own custom length.  Mig is a coldwelding process (compared to other processes) and sometimes has trouble burning thru nill scale.  I would also try going back to .023 wire if your doing1/8" material or thinner.  The thinner wire lets you take more time in makingthe bead which then allows you to put more heat into you metal, you can spend more time munipulating the weld puddle. I hope this helps.
Reply:Originally Posted by JayOI was wondering if you were running an extension cord? Also wondering if you were grinding of the mill scale?  If you were running a cord
Reply:Take a slice in the last half inch and see if the air pocket is still there. You may have enough pre-heat at that point to get penetration. I agree smaller wire so you can get more heat before the weld puddle gets so large that you move forward, this causes you to move before you get enough heat into the base to get the full fusion of the base metals and the filler. The wide base plate is acting like a heat sink taking away the heat before you get the penetration, so the puddle solidifies and builds before you want it to. Hopefully that makes sense.
Reply:how hot is it supposed to be getting? The bead and base metal are glowing read hot when i finish off the bead.
Reply:After all this discussion, maybe he should just stick weld it with 6010 and be done with it....MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by DesertRider33After all this discussion, maybe he should just stick weld it with 6010 and be done with it....
Reply:Originally Posted by DesertRider33After all this discussion, maybe he should just stick weld it with 6010 and be done with it....your heat is fine if your weld is penetrating like your picture shows.  i would focus on wire manipulation.  hard wire penetrates deeper in a pull, but your bead will be slightly narrower.  pushing lends itself to a flusher bead.  i would try two different approaches to see which suits you best.  first is small circles about the width of your desired bead maybe slightly smaller.  the second is a simple weave.i was discussing this with several of the welders at work.  the first question every time was, "how was he manipulating his wire?"
Reply:if i was arcing over the puddle, do you think that would cause the little pin whole or at least contribute to it? Some times (probably more than i realize)the puddle catches up and i arc on it.
Reply:I bet you couldn't break that piece no matter how hard you tried.  You did get fusion on the sides, but not into the root and beyond.More heat would solve your problem.   You said some places got better penetration than others, that points to operator.  Skip the weave and do a stringer right in the root.  Then make a second pass.Heat up the piece a little, then etch it again.  It will be more visible.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:It is good that you are looking at the details and wanting to know more.You are asking us to inspect a welment after it is already completed.That is NOT possible.Like others have already asked....Was the weldment prepared properly?Clean metal, "V" groove, and what was the angle of your torch?Were you dragging the torch? ETC.,.The travel speed of the wire thru the gun was given BUT what was your speed when welding the joint?I suspect that the travel speed was too high OR as others have said there was incomplete fusion because the joint was not "Vee'd" out and so there was not enough heat build up.
Reply:For MIG welding, the correct polarity is DC reverse (also known as electrode positive). Many wire welders come set for straight polarity (electrode negative), which is used for flux cored welding.  Is yours correct?You could also switch to 100% CO2 instead of the C25.  It will give you more penetration.  130 amps should give complete penetration on that 1\8" coupon.Last edited by 69 chevy; 03-12-2008 at 11:24 AM.
Reply:Originally Posted by 69 chevyFor MIG welding, the correct polarity is DC reverse (also known as electrode positive). Many wire welders come set for straight polarity (electrode negative), which is used for flux cored welding.  Is yours correct?